Conventionally, as disclosed in a patent document 1, a friction roller type transmission mechanism is known in which in order to prevent a radial pressing reaction from being directly inputted to a housing when the friction rollers are in frictional contact with one another, shafts of the friction rollers are bearing-fitted to common bearing supports on both sides of the friction rollers in an axial direction, wherein the bearing supports are attached to the housing, so that the friction rollers are rotatably supported with respect to the housing.
In such a friction roller type transmission mechanism, the radial pressing reaction, which is caused when the friction rollers are in frictional contact with one another, is canceled as an internal force within the bearing supports, and prevented from being inputted directly to the housing, thereby making it possible to reduce the weight of the housing because the strength of the housing does not need to be high.    Patent Document 1: JP 2002-349653 A